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Chemical reactors - reaction

  1. Oct 26, 2011 #1
    PER - chemical reaction

    Q: A reactor is needed to convert A to R in a liquid reaction. The stoichiomentry is simply A→R and the rate data is given in the table below (P5.21, Levenspiel 1999).


    For the reactant concentration to drop from CA0 = 1.3 mol/L to CAf =0.3 mol/L, determine,

    a) the time required with a batch reactor. (ans: 10.21 min).

    b) the volume required for a flow reactor to achieve the same conversion as in (a) and at
    a feeding rate of A 1000 mol/h in (1) a PFR, and (2) a CSTR. (ans: PFR V= 130.8 L;
    CSTR V = 25.6 L).

    c) the volumes of two flow reactors in series with the exit concentration of A from the 1st
    reactor xA1= 0.231 (i.e. CA1= 1 mol/L) for (1) 1st PFR +2nd CSTR, and (2) 1st CSTR
    +2nd PFR. For both cases, sketch the area for each reactor in the 1/rA-xA plot. (ans: 1,
    V1= 38.7 L,V2 17.9 L; 2, V1= 77.0 L, V2 = 85.4 L).

    Hints: Plot 1/rA vs. xA, calculate the area under the line, either by measuring the graphical
    area or by integration of the trend line equation (which should be a 5th order polynomial).


    This time, I cannot solve question (C).

    I can only calculate the part of CSTR.

    For the PER in case (1):

    (1000/60)(5.0244) (5.0244 is the area that from xA=0 to 0.230769, 1000/60 is the flow rate from part (B))

    My answer is wrong, but I don't know what's wrong with my calculation

    Last edited: Oct 27, 2011
  2. jcsd
  3. Oct 27, 2011 #2


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    Gold Member

    Are you sure about your data? I have the same textbook, and mine says 0.045 and 0.042 for the last two values of r
  4. Oct 27, 2011 #3
    Oh, thank you for reminding me. because I don't have the textbook.
    But, I still cannot find out the answer after using the right value.
    Is it wrong for me to plot a graph?
  5. Oct 27, 2011 #4


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    Gold Member

    I don't think there is anything wrong with fitting the data to a line and then integrating from 0.3 to 1.3 (which is one method that the hint does suggest), however i think it would be easier to just integrate numerically with approximating sums. Keep in mind that different methods will give different answers (my solution manual says 12.75 minutes).
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